Disasters: Oil Spills

Photo by: Nate A.

Liquid petroleum (crude oil and its refined products such as tar,
lubricating oil, gasoline, and kerosene) can be released as catastrophic
spills from point sources (e.g., from tankers and blowouts) or as chronic
discharges typically from nonpoint sources (e.g., from urban runoff or
fallout from the atmosphere). Releases of petroleum into the environment
occur naturally from
seeps
as well as from human sources. Together natural and human sources
contribute about 380 million gallons of petroleum to the oceans each year.
Of this, about 45 percent comes from natural seeps, and the remainder may
be attributed to the human activities of petroleum production,
transportation, and consumption. Discharges during petroleum production
tend to be restricted to areas of exploration and extraction and are
mostly due to the release of "produced waters" (water
extracted with petroleum from the reservoir); these discharges contribute
about 5 percent of the petroleum reaching the sea from human sources.
Spills during the transport, refinement, and distribution of petroleum are
most common along shipping routes and pipelines and make up about 22
percent of human-caused petroleum inputs. Spills during petroleum
consumption (i.e., use of automobiles, boats, etc.) tend to be small but
are so numerous and widespread that they contribute the vast majority
(about 70 percent) of human-caused petroleum pollution in the sea.
Therefore, consumers could make an enormous contribution to pollution
prevention through proper use of petroleum products in vehicles and other
personal equipment maintained to avoid leaks and spills.

The effects of spilled petroleum on marine organisms can be lethal or
sublethal. Lethal effects are often obvious after large spills, with the
most attention focused on birds and mammals (e.g., 900 bald eagles,
250,000 seabirds, 2,800 sea otters, and 300 harbor seals were killed
directly by the
Exxon Valdez
spill), but population-level consequences are difficult to measure.
Considerable controversy arises in the determination of when populations
have recovered. Even when organisms are not killed, oil fouling can reduce
feeding efficiency, growth and reproductive rates, survival of offspring,
and
resistance to diseases. Petroleum may act synergistically with other
pollutants, such as those found in urban runoff, to cause even more toxic
effects like high rates of mortality or reproductive failure. Petroleum
can kill birds and mammals by reducing the capacity of feathers and fur to
keep the animals warm, or through ingestion when birds and mammals attempt
to remove the petroleum or eat fouled prey.

The largest oil spill in history occurred from tankers, a tank field,
offshore terminals, and refineries during the 1991 Persian Gulf War; it
dwarfed other spills with a release of approximately 520 million gallons
of oil. This was more than three times the volume of the second-largest
spill, from the IXTOC 1 blowout in the Gulf of Mexico in 1979. The 1989
spill of eleven million gallons of crude oil from the
Exxon Valdez
along 1,100 miles of Alaska's pristine southern coast was the
largest spill in U.S. history and approximately the fortieth-largest spill
globally. It caused a national backlash against "big oil" in
the United States and led to the passage of the 1990 Oil Pollution Act.
This legislation creates a cooperative arrangement between the polluter
and the resource trustee in order to increase the speed and effectiveness
of cleanup efforts and reduce the intensity of litigation.

Oil spills from tankers capture the most media attention, but, as of 2000,
ships contributed less than 2 percent of petroleum in the oceans. This is
dwarfed by the 45 percent input from natural seeps. However, seeps
typically release oil at a slow constant rate and the surrounding
ecosystems have adapted to the presence of oil (although species diversity
is reduced), with microorganisms even using the oil as a source of energy.
Tanker spills, on the other hand, often occur in ecologically sensitive
near-shore areas and the volume of oil released at once can be
significant. The largest human source of petroleum in the marine
environment is the consumer, from sources such as personal watercraft
(especially two-stroke engines), automobiles, fuel jettisoned from
aircraft, and municipal waste, the sum of which aggregates into urban
runoff, wastewaters, river discharge, and atmospheric deposition. These
inputs are most pronounced in near-shore areas, which also have the most
sensitive ecosystems (e.g., estuaries, mangrove forests, coral and oyster
reefs, coastal marshes, sea grass, and kelp beds). These ecosystems derive
much of their physical structure from the organisms themselves; as such,
mortality due to petroleum can destroy the physical structure, leading to
erosion of underlying sediments and the collapse of the ecosystem.

Current technology is insufficient to clean up large spills. Techniques in
use include mechanical containment with
booms
and recovery with skimmers, suction equipment and sorbent materials,
chemical treatment with dispersing and gelling agents, and physical
removal via wiping, pressure washing, and raking. Scientists are
developing bacterial strains to devour petroleum in spills and fertilizers
to stimulate the success of these bacteria in the sea; although promising,
this technique remains insufficient. A 20 percent recovery of spill volume
is considered a good effort. Some cleanup efforts may do more harm than
good. For example, the hot water scouring of beaches following the
Exxon Valdez
spill stripped silt from between rocks and thereby prevented
recolonization by bivalves, which must wait until sediments are naturally
replenished. Some of the chemical agents are toxic themselves, and a
number, such as
gelling agents
, must be applied at several times the volume of the spill itself, clearly
impractical for a spill of millions of gallons.

Workers in orange coats standing on rocky beach using water hoses to
clean up the oil spill from the Exxon Valdez.
(

Courtesy of Richard Stapleton. Reproduced by permission.

)

It is still the case that most petroleum spilled is
"cleaned" by natural processes or remains for decades in the
environment in forms such as tarballs accumulated on shorelines or
petroleum soaked deeply into shoreline gravel. Natural cleansing of
petroleum in water, particularly light oils, occurs through evaporation
(10 to 75 percent during the first few days, depending on petroleum weight
and environmental conditions), photooxidation, and microbial degradation
by bacteria, fungi, and
heterotrophic phytoplankton
. A small amount dissolves in the water, but this increases the toxicity
of the water to organisms, and petroleum suspended in water may attach to
suspended sediments that eventually settle to the sea floor, from where
the petroleum may be rereleased into the water.

The monetary costs of petroleum spills vary tremendously, even for
identical spill volumes, depending on the sensitivity of the local
ecosystem, type of petroleum released, weather, ocean currents and waves,
time of year, use of local beaches, local fishing activity, presence of
ecological reserves, containment and cleanup effectiveness, and many other
factors. The financial responsibility for the spill lies with the
polluter, but the cost of a petroleum spill is open to interpretation and
often spawns litigation.

Spills from vessels in U.S. waters declined significantly during the 1990s
(less than one-third of total spillage in the 1980s) due to
better-designed ships (e.g., double-hull tankers and new construction
materials being phased in) and more stringent regulations and operational
practices. This decline in spills occurred at the same time as the global
tanker fleet grew slightly to 7,270 in 1999, but by that year more than
half of the fleet was less than fifteen

This table presents the ten largest oil spills since modern
compilations began in 1967. The volumes of many major oil spills,
especially those that occurred outside of North American or European
waters, were not precisely measured. Where the uncertainty is large
the range of possible spill volumes is given, ordered by the mid-range
estimate for the spill.

TEN WORST OIL SPILLS BY VOLUME, 1967–2002

Name

Location

Quantity (in millions of gallons)

Date

Arabian Gulf/Kuwait

Persian Gulf, Kuwait

380–520

January 19, 1991

IXTOC 1

Bay of Campeche, Mexico

140

June 3, 1979

Atlantic Empress

off Tobago

90

July 19, 1979

Kolva River

Kolva River tributary, Russia

84

September 8, 1994

Nowruz Oil Field

Persian Gulf, Iran

80

February 10, 1983

Castillo de Bellver

off Saldanha Bay, South Africa

79

August 6, 1983

Amoco Cadiz

Portsall, France

69

March 16, 1978

ABT Summer

off Angola

51–81

May 28, 1991

Haven

Genoa, Italy

45

April 11, 1991

Odyssey

off Nova Scotia, Canada

41

November 10, 1988

Prestige

off Spain

20

November 13, 2002

This table presents the ten largest oil spills since modern compilations
began in 1967. The volumes of many major oil spills, especially those
that occurred outside of North American or European waters, were not
precisely measured. Where the uncertainty is large the range of possible
spill volumes is given, ordered by the mid-range estimate for the spill.

years old. On the other hand, petroleum spilled from failed pipelines is
projected to increase as pipelines age. North America alone has 23,000
miles of petroleum pipelines. Similarly, as the human population grows and
consumes more petroleum, greater volumes of it will reach the seas from
consumptive sources.

All levels of society may contribute to reductions in petroleum pollution.
Governments can enact more stringent drilling, wastewater, transportation,
use, and recovery regulations and more rigorously enforce them.
Governments and industry can work together to ensure the integrity of the
pipeline system and reduce inputs from production activities. Improvements
can be made in the avoidance of spills, the tracking of vessels, including
their escort by tugs, and the general safety of a tanker fleet. Government
and industry can also partner to stop operational discharges such as
bilge
and fuel oil and oily
ballast
. Operational discharges are currently prohibited within fifty nautical
miles of the U.S. coast, but due to noncompliance and lax regulations in
many countries and international waters, these inputs are third in
importance only to land-based runoff and releases from two-stroke engines.
Consumers can use more efficient machinery that spills less petroleum,
such as four-stroke engines for personal watercraft, and can properly
dispose of petroleum products at recycling or collection centers. And
society can migrate away from fossil fuels to renewable sources of energy
that pose significantly fewer problems for both air and water pollution.

One of the most ecologically sensitive spots on earth was put at risk in
January 2001 when an oil tanker ran aground and capsized on San
Cristóbal Island in the Galápagos Islands. The
Galápagos, described by Charles Darwin as a living laboratory of
evolution, were spared when a fortuitous wind shift pushed some 170,000
gallons of diesel fuel out to sea and away from the fragile marine
reserve.

User Contributions:

wow this is terrible i was watching the news and a pelican broke its neck it just broke my heart when i seen this. There is a movie it is called agent cody banks and there was this guy and he was showing a modle of a thing similar to the oil spill and he thought of a robot that would suck up the oil and i thought it was a good idea and i think we should try it sometime

nice article .
I am working on research (Master degree) about concentration of aromatic and aliphatic hydrocarbons in water and sediment of the beach of raslanuf in libya .Could you please provide me with recent previous studies about this subject for instant in mexico gulf and other places , moreover I need references about petrolium pollution.

Thank you in advance

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